1

Nerve reaction:
It is possible that you are impinging parts of the nervous system with this maneuver. Tingling sensations(paresthesiae) certainly suggest a nerve type reaction and you should try modifying your stretching technique.
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2

Psoas Stretch:
The iliopsoas muscle starts up in the low back and pelvis and attaches into the femur. The tighter it becomes, the more anterior pelvic tilt occurs. Finding out how to check if it is tight and then do appropriate stretches 3 times per day is important. I attached a good video for you. Dr rich blake
http://youtu.Be/bht4192tklc.
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3

Good for you!:
Gentle stretching has been shown in studies to be surprisingly effective for back pain. Having the pain go away is a good sign and congratulations for sticking with your plan.
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7

Prolonged sitting:
Not for sure with only a little information, but with prolonged sitting, we can cause shortening of our psoas, leading to pulling in our back when we stand. This can be seen in people anywhere from being confined to a wheelchair to new office jobs to students cramming for tests. Try stretching by extending your legs at your hips. I hope that helps!
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8

Please see below:
Proximally, the psoas major muscle attaches to the 12th thoracic and to all of the lumbar vertebral bodies and the corresponding intervertebral discs and the transverse processes of the lumbar vertebrae. The iliacus attaches proximally to iliac fossa, the sacrum and the anterior sacroiliac ligaments. Distally, the two tendons merge forming the iliopsoas tendon to attach onto the lesser trochanter.
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10

Yes:
If it is inadequately drained or if ineffective antibiotics are used or if antibiotics are stopped too soon a psoas abscess can recur. These are frequently associated with discitis and vertebral osteomyelitis which if not adequately treated can lead to recurrence of the psoas abscess.
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